1. The Field of the Invention
The invention relates to devices, methods, and systems for signal amplification. Specifically, the invention relates to devices, methods, and systems for improving the gain precision and bandwidth of fixed-gain amplifiers.
2. The Relevant Art
During the previous century, the design and use of a myriad of electronic circuits has provided numerous timesaving technological advances to society. Communications, once painstakingly slow, now traverse vast distances at the touch of a button. Other laborious tasks are now performed, controlled, and monitored by machines and computers. Many of the complex machines and circuits used to perform these tasks are constructed of relatively simple building blocks or components. Of these components, one of the most basic and useful building blocks is the amplifier.
As electronic circuits and amplifiers continue to advance, there is a continual push for higher bandwidth and system capacity. In various applications, amplifiers with precisely specified gains and having very wide bandwidths are valuable building blocks. Applications, such as signal processing, active filter circuits, audio-to-digital converters, multi-level modulation, folding amplifiers, voltage buffers, and the like, require the use of wideband, precision, fixed-gain amplifiers to perform precision summing of analog signals and other functions.
Previously, the use of operational amplifiers in conjunction with negative feedback has been a standard approach to achieve stable amplifier gain despite changes in time, temperature, or other process variations. However, using negative feedback to increase amplifier stability can also result in degraded performance and bandwidth of the amplifier.
Many applications do not require excessive bandwidth, and therefore, conventional operational amplifier circuits may be sufficient. However, many applications, particularly applications within emerging markets, do require higher bandwidth and performance in addition to a certain degree of precision. In these cases, amplifiers comprising operational amplifiers using negative feedback may not provide sufficient performance and bandwidth needed in these applications.
Without using negative feedback for gain stabilization, the open-loop gain of an operational amplifier may measure in the thousands. Although an open-loop amplifier may be faster and have better bandwidth characteristics, a gain of this magnitude may be far too high and unstable to be useful in many applications. Additionally, the input of the amplifier must be kept extremely small to keep the output somewhat linear and to avoid saturation.
In some cases, operational amplifiers may be designed to have improved fixed-gain accuracy at much lower gains without using compensatory circuitry required with negative feedback. For example, an amplifier may achieve gain accuracy by accurately matching selected internal components. However, even with improvements at lower gains in gain accuracy, bandwidth, and performance, an undesirably large gain error (e.g. deviation from an ideal gain value) may be present that is unacceptable for many high-speed applications.
What is needed is apparatus and methods for improving the gain accuracy of fixed-gain amplifiers.
What is further needed is apparatus and methods for connecting multiple fixed-gain amplifiers to further improve the gain accuracy of any of the amplifiers operating independently.